Method of producing titanium



METHOD 6F PRODUCING TITANIUM Richard H. Singleton, Lexington, and PhilipJ. Clough,

Reading, Mass. assignors to National Research Corporation, Cambridge,Mass., a corporation of Massachusetts Application August 14, 1952,Serial No. 304,390

6 Claims. (Cl. 75-84.5)

This invention relates to the production of titanium metal or lowerchlorides of titanium, and more particularly to the production of puretitanium metal or pure titanium trichloride from titanium bearingmaterials.

It is a principal object of the present invention to provide an improvedprocess for manufacturing titanium from titanium bearing materials so asto obtain the titanium in a form essentially uncontaminated by theoriginal materials associated therewith.

Another object of the invention is to provide a relatively cheap processfor obtaining relatively pure titanium trichloride from titanium bearingmaterials such as titanium carbide.

Still another object of the invention is to provide a process of theabove type which is particularly adapted to the production of relativelypure titanium trichloride from titanium alloys.

Other objects of the invention will in part be obvious and will in partappear hereinafter. I

The invention accordingly comprises the process involving the severalsteps and the relation and the order of one or more of such steps withrespect to each of the others which are exemplified in the followingdetailed disclosure, and the scope of the application of which will beindicated in the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description, taken inconnection with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic flow sheet illustrating one embodiment of theinvention; and I r Fig. 2 is a diagrammatic flow sheet illustratinganother embodiment of the invention.

The present invention is primarily directed to the production oftitanium or lower chlorides of titanium from titanium bearing materials.vention is concerned with the use as starting materials of titaniumcarbide and titanium alloys. Of the alloys, copper-titanium alloys arepreferred, although other alloys such as the alloys of titanium withnickel can be employed. From the standpoint of cheapness and ease ofoperability of the process, the titanium-copper alloys are muchpreferred.

Titanium carbide and copper-titanium alloys can be relatively cheaplymanufactured by electric furnace reduction of titanium dioxide in thepresence of carbon. When the alloy is to be made, the alloying metal isalso present in the electric furnace charge. The use of titanium-copperalloys as a starting material in the present process will be discussedfirst. This alloy may be made by the arc furnace reduction of ilmeniteor the like with carbon in the presence of copper. Equally, it may bemade by dissolving impure titanium in molten copper.

A titanium-copper alloy from an electric furnace 8 (Fig. l) is fed to afirst high temperature reactor 10 which is arranged to hold the moltentitanium-copper alloy at a temperature above about 800 C. so as toprovidea large surface area for contact with hydrogen chloride vapors.At high temperatures on the order of In particular, the present intesExte 2,7s3..142 Patented Feb. 26, 1957 ice ' tial pressure is due to theoxidation of the titanium by the hydrogen chloride. Additionalhydrogen'is added to the reactor 10 as required, to maintain at leastthis ratio of 1 to 3.

The titanium in the titanium-copper alloy will react with the hydrogenchloride to form gaseous titanium lower chlorides at temperatures on theorder of 800 C. and above. However, it is preferred to operate at atemperature above the melting point of the titaniumcopper alloy. Thismelting point will vary with the changing composition of the alloy. As ageneral proposition it is preferred to operate at a temperature of about1000 C. or above so as to maintain the alloy molten at all times. Theprincipal (and idealized) reaction between titanium and hydrogenchloride is expressed by the following equation:

The gaseous reaction products from Equation A are preferably removedfrom the high temperature reactor as gases, and the condensible gasesare preferably condensed in a condenser 12, which may include amechanical scraper for removing the condensed solids. The uncondensedgases in the condenser will consist of titanium tetrachloride, hydrogenand hydrogen chloride. These gases are passed through a condenser 13 andthe titanium tetrachloride is separated therefrom. However, if thecondenser 12 is operated below 136 C., the titanium tetrachloride can becondensed along with the titanium dichloride and titanium trichloridecollected in the condenser. The unreacted hydrogen chloride and thehydrogen can be fed to a chlorine burner for converting most of thehydrogen to hydrogen chloride and the hydrogen chloride can then berecycled to the high temperature reactor. As will be apparent, someexcess hydrogen is recycled so as to provide the adequate partialpressure of hydrogen in the high temperature reactor 10.

The condensed solids from condenser 12 are next reacted in lowtemperature reactor 14 with titanium tetrachloride to assure a highconversion of the condensed solid products to titanium trichloride. As aresult of the condensing and the reaction with titanium tetrachloride,essentially all of the titanium is in the form of titanium trichloride.A number of reactions take place during the process of condensing andreaction with the,

titanium tetrachloride. Titanium trichloride leaving the hightemperature reactor 10 may disproportionate to titanium dichlorideduring the condensing. Thus, the initially condensed products maycomprise titanium trichloride, and titanium dichloride, gaseous titaniumtetrachloride being given off during this condensing as a result of thedisproportionation. While the condensing has been shown as thepreferredv cooling step at 12 in Fig. 1,; this cooling may be achievedby shock-cooling as shown at 12a in Fig. 2 and discussed more fullyhereinafter.

The titanium dichloride is converted to titanium trichloride by reactionwith titanium tetrachloride in accordance with the following equation:

101 TlCh m arrest.) a

titanium trichloride in a state of high purity. This retetrachloride andmay be transported to a suitable 'condenser 16 for condensing thetitanium trichloride as a solid. While one reactor 14 has been shown forachieving conversion of the titanium dichloride to titanium trichlorideand for subliming this trichloride-thisreactor may comprise two separatepieces of equipment. Equally, the conversion of titanium dichloride totitanium trichloride may be achieved at a higher temperature (on theorder of 600 C. to 800 C.) during the sublimation of the titaniumtrichloride.

In Fig. 2 the titanium carbide is fed to the high temperature reactorwhere it is reacted at a high temperature above about 1000 C. withhydrogen chloride vapor. The vapors leaving the high temperature reactorcomprise unreacted hydrogen chloride, titanium trichloride, perhaps sometitanium dichloride, some titanium tetrachloride and hydrogen. Thecondensable portions of these vapors may be condensed or shock-cooled(by use of cold hydrogen or argon) preferably to a temperature below 500C. in a shock cooling zone 12a. The shock-cooled solid products(comprising primarily titanium trichloride, and titanium dichloride) arefed to the low temperature reactor 14 where they are reacted withtitanium tetrachloride in a manner similar to that discussed inconnection with the process of Fig. 1 to form titanium trichloride.

Both of the above processes result in high yields of essentially puretitanium trichloride. This titanium trichloride may be converted totitanium metal by a number of techniques, such as in an electrolysiscell (Fig. 1.) which may be of the type described more fully in thecopending application of Banner and 'Chadsey, Serial No. 233, 204, filedJune 23, 1951.

As can be seen from Fig. 1, the electrolysis of a solution of titaniumtrichloride will yield chlorine at the anode along with some titaniumtetrachloride, the yield of titanium tetrachloride being dependent uponthe amount of titanium trichloride in solution at the anode. At thecathode the titanium trichloride is electrolyzed to titanium metal. Thechlorine generated in the electrolytic cell may, as shown, be combinedin burner 22 with the hydrogen resulting from the high temperaturereactor to form additional hydrogen chloride for recycling to the hightemperature reactor. It is of course obvious that, depending uponeconomic considerations, it may be more desirable to sell the resultanthydrogen and chlorine separately than to recombine these materials togenerate hydrogen chloride. This naturally will depend 'to a largeextent on the relative cost of hydrogen, chlorine, and hydrogen chlorideat any plant location.

The titanium tetrachloride resulting from the electrolysis of thetitanium trichloride may be recycled to the low temperature reactor 14or perhaps recycled to the high temperature reactor (along with thehydrogen chloride) depending upon how much excess titanium tetrachlorideis obtained from the electrolytic cell. As mentioned previously, theproduction of titanium tetrachloride in the electrolytic cell is afunction of the amount of titanium trichloride in solution in thevicinity of the anode. This quantity may be greatly reduced by the useof bafiies, diaphragms, and the like in the electrolytic cell.

Equally, the titanium trichloride may be converted to titanium metal,such as by the use of a disproportionation apparatus 24 '(Fig. 2) of thetype described and claimed more fully in the copending application of Al. Singleton and van Arkel, Serial No. 285,975, filed May 3, 1952.

When disproportionation is used for converting the titanium trichlorideto titanium, considerable quantities of titanium tetrachloride aregenerated. This titanium tetrachloride may be converted to titaniumtrichloride and hydrogen chloride in a suitable apparatus 26 (Fig. 2)therefor by passing titanium tetrachloride and hydrogen over a surfaceheated to approximately 1200 C. or higher. The titanium trichloride isrecycled to the disproportionation apparatus 24, while the resultanthydrogen chloride is recycled to the high temperature reactor. Since theconversion of titanium tetrachloride to titanium trichloride is notquantitative it is necessary to employ recycle of the titaniumtetrachloride and hydrogen leaving the reduction apparatus 26. Thisrecycle of titanium tetrachloride is not shown on Fig. 2, but may bereadily accomplished by condensing titanium tetrachloride in theoutgasses.

It is also necessary to strip the hydrogen chloride from the hydrogen(at 28) before recycling the hydrogen through the hydrogen reductionapparatus. This may be readily achieved by low temperaturerefrigeration. The stripper 23 has been shown as a single step but willactually comprise several separate pieces of equipment, the condensedhydrogen chloride being revaporized for recycle into the hightemperature reactor 10. In connection with the hydrogen reduction oftitanium tetrachloride to titanium trichloride, it has been found thatsmall amounts of aluminum trichloride vapors in the stream of titaniumtetrachloride and hydrogen vapors greatly catalyzes the conversion oftitanium tetrachloride to titanium trichloride.

In addition to the above techniques, the titanium trichloride may bethermally reduced to titanium metal by the use of reducing agents, suchas sodium, magnesium and the like. Alternatively, the titaniumtrichloride may be chlorinated to produce pure titanium tetrachloridefor use in thermal reduction processes, such as those shown in the Krollpatent No. 2,205,854, Maddex patent No. 2,556,763, or in the torchprocess described and claimed more fully in the copending application ofFindlay, Serial No. 200,606. 7

' When converting the titanium trichloride to titanium tetrachloride, itis preferred to operate at a temperature slightly above the boilingpoint of titanium tetrachloride (i. e., above 136 C.) so as to removethe titanium tetrachloride from the reaction zone as fast as it isformed. In this case it is also possible to eliminate the lowtemperature reactor since titanium dichloride is highly reactive withchlorine.

In the preferred form of apparatus employed with the above discussedinvention, the various high temperature portions of the reactor arepreferably formed of graphite or carbon. When carbon or graphite isused, the necessary heat input can be readily achieved by using thecarbon or graphite as an electrical heating element in either aninduction or resistance heating circuit. Where mechanical movement isrequired in the high-temperature portions, it is preferred to employrefractory metals, such as molybdenum, for those parts requiringhightemperature mechanical strength or wear resistance. Those portionsof the apparatus which operate at temperatures of about 600 C. or lowercan be formed of stainless steel, nickel or refractory metals, such asmolybdenum and the like. Carbon and graphite can equally be used in therelatively low-temperature portions of the apparatus, but, formechanical reasons, may be less preferred than the metals in many cases.

In general, the high temperature reactor may be a countercurrent still,similar to a zinc still, or a rotary kiln. Both of these arrangementsfurnish a large surface area for the titanium-copper alloy to be reactedwith the hydrogen chloride. The still type of apparatus is preferredwith the molten alloy while the rotary kiln type is preferred with thesolid titanium carbide. When shock cooling is employed it may take placein a portion of the high temperature reactor. In this case theshock-cooled products may be removed from the high temperature reactoras solids. Equally, the shock-cooling or condensing may take placeoutside of the high temperature reactor as illustrated on the attachedflow sheets.

When a titanium-copper alloy is used, the percentage of titanium in thealloy is preferably in the range of 40% titanium to 60% titanium, thepercent titanium being reduced to about before the copper is recycled tothe electric furnace for addition of more titanium.

In connection with the above discussed embodiments of the invention itshould be pointed out that, on a recycle basis, there may be either anexcess or shortage of titanium tetrachloride. If there is an excess oftitanium tetrachloride, this may be reduced to titanium trichloride asshown at 26 in Fig. 2. If there is a shortage of titanium tetrachloride,which might result in an excess of titanium dichloride, this dichloridecan be chlorinated to titanium trichloride.

In connection with the above discussion of the present invention, littleemphasis has been placed on the shockcooling requirements. It should bepointed out that the shock-cooling gases must be free of oxygen,nitrogen and compounds thereof such as water vapor, carbon monoxide andthe like. This is due to the extreme reactivity of titanium and itschlorides with oxygen and the like. The great mass of cold hydrogen orargon required to shock-cool the hot reaction products necessitates highpurity for these gases and, as a consequence, these gases are preferablyused on a recycle basis with any necessary purification apparatus in therecycle system.

While resublimation of the product titanium trichloride in the lowtemperature reactor 14 has been set forth as a highly desirable step inthe process it is not essential in all cases. This is particularly truewhere this titanium trichloride is essentially pure or sufficiently purefor its sub sequent use. This purity will naturally depend upon thepurity of the starting materials and the degree of carryover ofcontaminants from the high temperature reactor to the cooling zone. Thepurity requirements of the titanium trichloride willvary considerablywith the details of the further processing steps. For example, ifdisproportionation is to be employed, the titanium trichloride must havea very high purity. If the subsequent step is chlorination to titaniumtetrachloride the titanium tri chloride need not be particularly pure,provided the contaminants can be separated from titanium tetrachloride.With regard to electrolysis the purity requirements will be largelydependent upon the solubility of the impurities in the moltenelectrolyte.

Since certain changes may be made in the above process, withoutdeparting from the scope of the invention herein involved, it isintended that all matter contained in the above description, or shown inthe accompanying drawings, shall be interpreted as illustrative and notin a limiting sense.

What is claimed is:

1. The process of manufacturing titanium trichloride which comprisesforming a crude alloy of titanium and copper, heating said alloy in areaction zone to a temperature above about 800 C., contacting said hotalloy with hydrogen chloride to convert said titanium to gaseoustitanium trichloride, maintaining in the reaction zone at least one moleof hydrogen for each three moles of hydrogen chloride, and removinggaseous titanium trichloride from the reaction zone.

2. The process of manufacturing titanium which com prises forming acrude alloy of titanium and a second metal selected from the classconsisting of copper and nickel, heating said alloy in a reaction zoneto a temperature above about 1000 C., contacting said hot alloy withhydrogen chloride to convert said titanium to a gaseous lower chlorideof titanium and to convert said hydrogen chloride to hydrogen, passingthe gaseous products from the reaction zone, cooling the gaseousproducts leaving the said reaction zone to a temperature below about 500C., heating the cooled products to a temperature of about 600 C. in thepresence of titanium tetrachloride to sublime titanium trichloride,condensing said sublimed titanium trichloride, and converting saidtitanium trichloride to titanium metal.

3. The process of manufacturing titanium trichloride which comprisesheating a titanium bearing material in a reaction zone to atemperature'above about 800 C., said titanium bearing material beingselected from the class consisting of titanium carbide and a titaniumalloy of a second metal selected from the class consisting of copper andnickel, contacting said hot titanium bearing material with hydrogenchloride to convert said titanium to a gaseous lower chloride oftitanium and to convert said hydrogen chloride to hydrogen, passing thegaeous products from the reaction zone, cooling the gaseous productsleaving said reaction zone to a temperature below about 500 C., heatingthe cooled products to a temperature of about 600 C. in the presence oftitanium tetrachloride to sublime titanium trichloride, and condensingsaid sublimed titanium trichloride.

4. The process of claim 3 wherein the gaseous products leaving the hightemperature reaction zone are shockcooled to reduce the amount ofdisproportionation of titanium trichloride during cooling.

5. The process of manufacturing titanium trichloride which comprisesheating titanium carbide in a reaction zone to a temperature above about1000 C., contacting said hot titanium carbide with hydrogen chloride toconvert said titanium carbide to a gaseous lower chloride of titaniumand to convert said hydrogen chloride to hydrogen, passing the gaseousproducts from the reaction zone, cooling the gaseous products leavingsaid reaction zone to a temperature below about 500 C., heating thecooled products to a temperature of about 600 C. in the presence oftitanium tetrachloride to sublime titanium trichloride, and condensingsaid sublimed titanium trichloride.

6. The process of manufacturing titanium trichloride which comprisesheating titanium-copper alloy in a reaction zone to a temperature aboveabout 800 C., contacting said hot titanium-copper alloy with hydrogenchloride to convert said titanium-copper alloy to a gaseous lowerchloride of titanium and to convert said hydrogen chloride to hydrogen,maintaining in said reaction zone a ratio of partial pressures ofhydrogen to hydrogen chloride of at least 1 to 3 to inhibit formation ofcopper chlorides, passing the gaseous products from the reaction zone,cooling the gaseous products leaving said reaction zone to a temperaturebelow about 500 C., heating the cooled products to a temperature ofabout 600 C. in the presence of titanium tetrachloride to sublimetitanium trichloride, and condensing said sublimed titanium trichloride.

References Cited in the file of this patent UNITED STATES PATENTS1,173,012 Meyer et a1 Feb. 22, 1916 2,519,385 Loonam Aug. 22, 19502,607,675 Gross Aug. 19, 1952 2,618,549 Glasser et al Nov. 18, 19522,647,826 Jordan Aug. 4, 1953 2,670,270 Jordan Feb. 23, 1954 2,694,652Loonam Nov. 16, 1954 OTHER REFERENCES Comprehensive Treatise onInorganic and Theoretical Chemistry, by Mellor, vol. 7, pages 74-77.Published 1927 by Longmans, Green & Co., 55 Fifth Avenue, New York.

Titanium, by Barksdale, page 8.1. Published 1949 by The Ronald PressCo., New York.

1. THE PROCESS OF MANUFACTURING TITANIUM TRICHLORIDE WHICH COMPRISESFORMING A CRUDE ALLOY OF TITANIUM AND COPPER, HEATING SAID ALLOY IN AREACTIN ZONE TO A TEMPERATURE ABOVE ABOUT 800*C., CONTACTING SAID HOTALLOY WITH HYDROGEN CHLORIDE TO CONVERT SAID TITANIUM TO GASEOUSTITANIUM TRICHLORIDE, MAINTAINING IN THE REACTION ZONE AT LEAST ONE MOLEOF HYDROGEN FOR EACH THREE MOLES OF HYDROGEN CHLORIDE, AND REMOVINGGASEOUS TITANIUM TRICHLORIDE FROM THE REACTION ZONE.
 2. THE PROCESS OFMANUFACTURING TITANIUM WHICH COMPRISES FORMING A CRUDE ALLOY OF TITANIUMAND A SECOND METAL SELECTED FROM THE CLASS CONSISTING OF COPPER ANDNICKEL, HEATING SAID ALLOY IN A REACTION ZONE TO A TEMPERATURE ABOVEABOUT 1000*C., CONTACTING SAID HOT ALLOY WITH HYDROGEN CHLORIDE TOCONVERT SAID TITANIUM TO A GASEOUS LOWER CHLORIDE OF TITANIUM AND TOCNVERT SAID HYDROGEN CHLORIDE TO HYDROGEN, PASSING THE GASEOUS PRODUCTSFROM THE REACTION ZONE, COOLING THE GASEOUS PRODUCTS LEAVING THE SAIDREACTION ZONE TO A TEMPERATURE BELOW ABOUT 500* C., HEATNG THE COOLEDPRODUCTS TO A TEMPERATURE OF ABOUT 600*C. IN THE PRESENCE OF TITANIUMTETRACHLORIDE TO SUBLIME TITIANIUM TRICHLORIDE, CONDENSING SAID SUBLIMEDTITANIUM TRICHLORIDE, AND CONVERTING SAID TITANIUM TRICHLORIDE TOTITANIUM METAL.